Crabs Burrow Into Controversy

Researchers Look Into Plight Of The Horseshoe Species

BLACKSBURG — They look like creatures from a science fiction film, with round, dark brown shells and a spiky tail.

They have two sets of eyes and five pairs of legs. Their blood is as blue as the ocean they call home.

"They are totally unique," said Stephen Smith, director of the Aquatic Medicine Laboratory at the Virginia-Maryland Regional College of Veterinary Medicine.

Horseshoe crabs may look like they come from another planet.

But the durable animals play a significant role in Atlantic coast environment. They are valuable resources for commercial fishermen and the biomedical industry.

And with conservationists raising concerns about a decline in the horseshoe crab population, the crustaceans have burrowed their way into the middle of one of the East Coast's hottest environmental controversies.

Virginia Tech fisheries and wildlife professor Jim Berkson and graduate student Elizabeth Walls have waded into the debate. The two have conducted a series of studies designed to improve management of the crab population and reduce conflicts between conservationists and those who harvest horseshoe crabs for commercial use.

Conservationists have taken an interest in the issue because a dozen species of migratory shorebirds feed on the crabs' eggs.

The plight of the horseshoe crab "has become a crisis in the last five years," Berkson said. "The Audubon Society and other environmental organizations are becoming concerned."

Berkson said fisheries management agencies need better information about the population and the movements of horseshoe crabs to impose appropriate limits on fishermen, who harvest horseshoe crabs for bait.

Biomedical companies, which harvest crabs for their blood and return them to the sea, need the information to reduce the species' mortality rate, Berkson added.

"This is not an endangered species," he said. "There are millions of horseshoe crabs out there. But, clearly, the population is declining."

Horseshoe crabs have existed for more than 350 million years. From the 1880s through the 1960s, they were caught and ground for fertilizer. Commercial fisheries still capture about 3 million crabs a year and use them as bait for eel and conch.

"This was considered a garbage species," Walls said.

Conservationists worry that the horseshoe crab population along the Atlantic coast will plummet, causing a similar decline in the number of migrating shorebirds that eat the crabs' eggs during their annual northward flights.

In response to those concerns, the Atlantic States Marine Fisheries Commission in February approved a 25 percent reduction in horseshoe crab harvests along the entire coast from Maine to Florida.

The reduction could have a significant impact in Virginia, which had allowed the capture of up to 710,000 horseshoe crabs as recently as last year.

"(The commission has) to manage these things effectively, and they don't have the information they need," said Berkson, who served on an expert committee that reviewed the commission's 1998 horseshoe crab management plan.

Berkson hopes the information he and Walls generate will help fisheries' management agencies.

"The sky's the limit for what needs to be known about these guys," said Berkson, who joined the faculty in Tech's College of Natural Resources in 1998.

His three-year, $125,000 research project is funded by BioWhittaker, a Maryland-based company that harvests horseshoe crabs for their blue blood.

Unlike iron-based blood, which is red, the horseshoe crab's blue blood has a copper base.

Biomedical companies extract the blood to obtain a clotting agent called Limulus Amebocyte Lysate. The agent is used to detect the presence of bacteria in injectable drugs and implantable medical devices such as pacemakers.

A quart of horseshoe crab blood can fetch up to $15,000, according to biomedical industry analysts.

The fisheries commission requires BioWhittaker and other biomedical companies to tag a portion of the crabs they harvest for bleeding and estimate how many are killed during the process.

As part of their research for BioWhittaker, Berkson and Walls will collect information on the size, sex and approximate age of the crabs they tag. Berkson said that information is vital to improving the management of the species.

Walls spent last summer on the island of Chincoteague, just south of the Maryland border, tagging crabs in an attempt to better track their movement and survival.

She and Berkson brought about 30 of the crabs back to Blacksburg, housing them in tanks at the Virginia-Maryland Regional College of Veterinary Medicine.

The female crabs have since spawned, producing hundreds of crabs that are kept in tanks throughout the college's Aquatic Medicine Laboratory.

Horseshoe crabs take 10 years to reach maturity and have a life span of 15 to 20 years, researchers said.

With funding from the Virginia Sea Grant College Program, Berkson and Smith are analyzing the chemistry of the crab's blood.

They also are trying to determine how much blood scientists can extract from the crabs without hurting the creatures' chances for survival.

About 15 percent of the crabs captured for biomedical purposes die after their blood is extracted, Berkson said.

Horseshoe crab experts and fisheries management officials agree on the need for better information about the plight of the horseshoe crab.

"The time is ripe to set something in place rather than continue the helter skelter harvesting that's going on up and down the East Coast," said Carl Shuster, an adjunct professor at the Virginia Institute of Marine Science, who has studied the species for nearly 50 years.